Docker Basic Commands

Question 1

How to download a Docker image from docker hub?

Answer 1

docker pull "image-name"
e.g. docker pull ubuntu 
docker pull ubuntu:16.04 
docker pull busybox 
docker pull centos:6

Question 2

What’s the command to see offline Docker images?

Answer 2

docker images

Question 3

What’s the command to see running Docker containers?

Answer 3

docker ps
OR
docker container ps

Question 4

What’s the command to see all Docker containers?

Answer 4

docker ps -a | docker ps –all

Question 5

How to run a docker container from a docker image?

Answer 5

docker run -it "Image-name" "optional command"
e.g. docker run -it busybox
docker run -it busybox ls
docker run -it busybox echo "Hey there!"
docker run -it ubuntu:16.04

Question 6

Command to know the number of docker images, Containers and other general Docker info?

Answer 6

docker info

Question 7

How to get into a docker container?

Answer 7

• Ensure container is running
• Provide the following command
  docker exec -it “Container-ID” “Command”
  e.g. docker exec -it ubuntu:16.04 /bin/bas

Question 8

What are the stages of “run” command

Answer 8

run command = create container + start container
so “docker run -it busybox” is equivalent to

docker create “image name”
docker create busybox – provides you a long alphanumeric key
and
docker start -a “alphanumeric key”

“-a” is for displaying the output on screen (STDOUT) when that container starts, else there will be no output

Question 9

What if you forgot to use -a with “docker start” command, how can you still see the output of docker start?

Answer 9

Yes, by using “docker logs” command.

Question 10

What does “docker system prune” command does?

Answer 10

“docker system prune” removes all the “stopped” docker containers and resources like cache, network and images used by these containers

Question 11

How to stop the running container?

Answer 11

Using “docker stop container-id”

Question 12

Which Docker command is used to execute terminal commands in a running container?

Answer 12

docker exec -it “container-id” “terminal command”
e.g
docker exec -it 28d73bdcb05e /bin/bash
If you need to put this process in the background, use -itd, instead of just -it. “d” here is deamon means background process.